Chapter 22.2, Problem 7R

To determine

To Compare: A dilute solution of a strong acid and a concentrated solution of a weak acid.

Explanation of Solution

Introduction: Acid is a substance which has a tendency to produce hydrogen ions when dissolved in water.

The number of ${\text{H}}^{+}$ ions that an acid produces in an aqueous solution determines its strength. The greater the number of ${\text{H}}^{+}$ ions produced in the aqueous solution, the stronger is the acid.

Acids which ionizes almost completely in aqueous solutions producing a large number of ${\text{H}}^{+}$ ions are termed as strong acids.

Acids which ionizes to a small degree at ordinary dilution to give low concentration of ${\text{H}}^{+}$ ions are termed as weak acids.

Therefore, greater the degree of dissociation of the acid, the stronger is the acid.

The concentration of a solution is related to the amount of acid dissolved in the solution.

On diluting an acid, the ionization of an acid increases therefore, concentration of ${\text{H}}^{+}$ ions or ${\text{H}}_3{\text{O}}^{+}$ ions increase. Thus, the strength of any acid increases with dilution.

A strong acid produces a large number of ${\text{H}}^{+}$ ions. On dilution, it will produce more number of ${\text{H}}^{+}$ ions. Thus a strength of a strong acid increases on dilution.

However, a concentrated solution of a weak acid produces a low concentration of ${\text{H}}^{+}$ ions as the acid dissociates only partially in the given aqueous solution.

Therefore, the acidic strength of a dilute solution of a strong acid is more than a concentrated solution of a weak acid.

Conclusion: A dilute solution of a strong acid is more acidic than a concentrated solution of a weak acid.